Brakes



NOV. 22, T. s TAYLQR ET AL BRAKES 5 Sheets-Sheet 1 Filed D90. 51, 1964 Inventors NOV. 22, 1966 T, s TAYLOR ET AL 3,286,798

BRAKES Filed Dec. 31, 1964 5 Sheets-$heet 2 Inventors Thomas S.Tm5 ior Frederick R. Ling;

13 WWW, KW Md Dm/ fl'lr'korrzeg' Nov. 22,1966 s TAYLOR ET AL 3,286,798

BRAKES Filed Dec. 51, 1964 5 Sheets-Sheet 5 Inventors Thomas 6. Ta u Jor' Frederick R. Lin-g/ 5 M 20 Mm! .DM

United States Patent 3,286.798 BRAKES Thomas S. Taylor, Suffern, N.Y., and Frederick Raymond Ling, New Milford, N.J., assignors to Abex Corporation, a corporation of Delaware Filed Dec. 31, 1964, Ser. No. 422,613 6 Claims. (Cl. 188-195) This invention relates to a package brake unit for railroad cars, and more particularly, to a package brake unit adapted to provide a proportional braking force with changes in loading of the railroad car.

The present invention relates to a so-called package brake unit which is characterized by an individual air cylinder or cylinders carried by each trunk of the railroad car. Preferably, the package brake unit is mounted on a spring supported bolster so as not to be subjected to direct rail shock, and so as to move vertically with respect to the truck side frames, as the loading of the railroad cars change.

It is particularly advantageous to employ the standard component brake beams for applying the braking force to the railroad cars and to employ familiar brake beam operating mechanisms, including a live lever, connecting rod and dead lever for operating the standard brake beams. Accordingly, an object of the present invention is to adapt a package brake unit to provide proportional braking force by eliminating the standard pin type of connection between the piston of the cylinder and the live lever; and providing in lieu thereof, a camming plate atfixed to the end of the piston for operating the live lever to apply the brakes, thereby permitting the camming plate and piston to move vertically with respect to the live lever, so that changes are effected in lever ratios to give changes in braking force with changes in car loading.

Another object of the invention is the maintaining of the piston stroke at a constant stroke by providing the camming plate with a tapered surface adapted to maintain the piston stroke at a constant value, which if not maintained, may adversely affect the braking force being generated.

A slack adjuster assures the proper stroke of the piston when the piston is moved to cause application of the brake shoes to the car wheels. However, when the brake shoes are applied by a hand brake mechanism, the piston is not moved. Accordingly, a further object of the invention is to connect a slack adjuster to the live lever and dead levers to prevent operation of the slack adjuster to compensate for a short or no piston stroke during a braking operation when the live lever is operated by a hand brake linkage.

According to the preferred embodiment of the invention, a truck of a railroad car is provided with a package brake unit including a fluid cylinder operable to move a piston to operate a brake linkage. The piston has secured thereto a tapered camming plate which is adapted to engage a live lever and to rotate the live lever about its pivotal connection on a brake beam strut. The live lever is operable to translate its associated brake beam to produce brake shoe engagement with a first set of car wheels to apply a frictional retarding force to a first set of car Wheels, and the live lever is operable through a connecting rod to pivot a dead lever to move brake shoes of a second brake beam against a second set of railroad car wheels. The camming plate is free to move with move ment of the bolster in a vertical direction relative to the live lever. The point of application of the operating force by the camming plate on the live lever is changed with changes in car loading; and, thereby, also changed are the effective lever ratios and the amount of braking force applied to the car wheels. A slack adjuster is disposed 3,286,798 Patented Nov. 22, 1966 in axial alignment with the cylinder and is operably connected to the live and dead levers to maintain a constant piston stroke and to compensate for changes in brake shoe size. A one way connection is provided between the live lever and slack adjuster for operation of the slack adjuster by a hand brake mechanism to prevent adjustment by the slack adjuster for lack of movement of the piston during a hand brake operation.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principle thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

FIG. 1 is a perspective view of a truck of a railroad car provided with a package brake adapted to provide a proportional braking force, according to the present embodiment of the invention;

FIG. 2 is a front elevational view of the camming plate and live lever;

FIG. 3 is a rear elevational view of the dead lever and slack adjuster housing;

FIG. 4 is a plan view of the package brake unit adapted to provide a proportional braking force;

FIG. 5 is a front elevational view of the camming plate and liver lever; and

FIG. 6 is a plan view of a camming plate and liver lever.

Referring now to the drawings, and more particularly to FIG. 1, there is illustrated a conventional truck 10 adapted to support one end of a body (not shown) of a railroad car. The car body is supported for swivel movement on a pair of spaced side bearings 12 on a centrally disposed bolster 13 disposed between truck side frames 14. The truck side frames 14 have a pair of axles 15 disposed therebetween and journaled therein, and onthe axles 15 are mounted spaced car wheels 16.

The bolster 13, which supports the car body, is supported on coil springs 18 on each of the truck side frames 14 and is thereby isolated to a certain degree from the rail shocks transmitted by the wheels 16 directly to the truck side frames 14. Also, because the weight of the car body (not shown) is borne directly by the bolster, the bolster 13 moves downwardly to compress the coil springs 18, as the load on the railroad car body is increased. Conversely, with a decrease in the loading of the car body, the coil springs 18 expand .and move the bolster 13 vertically upward with respect to the side frames 14. V

The package brake unit including an air cylinder and piston means 20 are of the type designated by the reference character 21, in co-pending application, Serial No. 226,924, filed September 28, 1962, now Patent No. 3,177,- 984 and entitled Bolster Mounted Brake Unit, the subject matter of which is incorporated herein by reference, and is made a part hereof, as if fully reproduced herein. In the present invention, the cylinder and piston means 20 are operable to actuate a live lever 22, to cause a braking operation in the same manner as in the co-pending application, except that the live lever 28 of the copending application is connected by a universal joint to a push rod. In fact, it is an important aspect of the present invention that the live lever not be directly connected to the push rod which would act on the live lever 22 at the same point of contact in all positions of bolster movement, as was the case of the co-pending application.

More specifically, the piston and cylinder means 20 has a piston 24 to which is secured a camming plate 25, FIG. 6, by a pair of spaced cap screw fasteners 26-. As best seen in FIG. 6, operation of the cylinder and piston means 20 moves the camming plate 25 thereon from the full line position to the dotted line position, during which movement, the camming face 30 of the camming plate 25 will engage a surface 31 on the live lever 22, and will pivot the live lever 22. I p

As best seen in FIG. 4, pivotingof the live lever 22 by the camming plate 25 causes the live lever 22 to pivot about a pivot pin connection or fulcrum point 32 in strut 33 of a brake beam means 34-. The pivoting of the live lever 22 in a counterclockwise direction, as seen in FIG, 4, is accompanied by a thrusting of a connecting rod 36 rearWardlTy. The connecting rod 36 is connected by a clevis 37 and pin 38 to a lower end 39 of the live lever 22, and the connecting rod 36 is disposed under the bolster 13, so as to be called a rod-under type. The connecting rod 36 is provided with a clevis 40 at its rearward end and is pinned to a dead lever 42 by a pivot pin 43.

The dead lever 43 is pivotally mounted on a pivot pin 44 in a strut 45 of a second brake beam means 46. The upper end 48 of the dead lever 42 acts against a pin 50 of a clevis 51 of a rack 52 extending rearwardly from a slack adjuster 53.

As will be readily understood by those familiar with the art, the live lever 22, dead lever 42 and connecting rod 36 are essentially of the conventional configuration and the arrangement employed to operate the conventional type of brakebeams 34 and 46, which have been standard in the industry for many years. Thus, it will be understood that rotation of the live lever 22 in a counterclockwise direction, as seen in FIG. 4, by the camming plate 25, causes the brake beam 34 to translate forwardly to bring opposed brake shoes 55 thereon into engagement with the treads 56 on one pair of car wheels 16. Simultaneously, the rearward thrust of the connecting rod 36 by the live lever 22 causes the dead lever 42 to rotate counterclockwise about the pin 44 and to translate the brake beam 46 rearwardly to engage brake shoes 58 on brake beam 46 against the treads 56 of a pair of rear car wheels 16. The brake beams 34 and 46 may be either mounted by conventional hangers or disposed for slidable translation in so-called Unit beam slots on the side frames 16.

In addition to being operated by the cylinder and piston means 20, the live lever 22 can also be operated by a hand brake linkage which includes a link 60, FIG. 4, connected by a clevis 61 and pin 62 to the upper end of the live lever 22. The hand brake link 60 is connected to a lever 64, which is mounted on a pivot post 63, and the lever 64 is rotatable by a handbrake pull rod 65 leading to a conventional handbrake operating means on the 'body of the car. The pivoting of the live lever 22 by either the cam plate 25 or link 60 causes a counterclockwise rotation of the live lever 22, as seen in FIG. 4, and a translation of the brake drum beams 34 and 46 to apply the brake shoes 55 and 58 against the treads 56 of the car wheels 16. For reasons which will be hereinafter explained in detail, it is necessary to provide a one way or connecting rod means 68 between the slack adjuster 53 and the live lever 22, so that upon operation of braking mechanism by the hand brake mechanism, the slack adjuster does not try to compensate for the lack of movement of the piston when the slack adjuster 53 is acted upon by a force exerted on the rod 52 by the dead lever 42.

As has been brought out hereinbefore, the piston and cylinder means 20 and camming plate 25 are adapted to move vertically with the bolster 13 upon changes in loading of the car disposed on the bolster 13. Since the camming plate 25 is not directly connected to the live lever 22, but is normally disposed at a slight distance therefrom and is movable into engagement therewith, the camming plate 25 is adapted to have its intersecting or contacting point with the live lever 22 changed with vertical move= ments of the bloster resulting from changes in car load ing. More specifically, as seen in FIG. 5 th e lower end of the camming plate 25, whe in the full line position, is adapted to intersect the live lever 22 at a contact point 28. In this position, the car is lightly loaded and the bolster 13 is in its upper position and the effective length of the lever arm for operating the brake beams and 46 is from the contact point 28 to the pivot pin 38. How= ever, as the car weight is increased and the bolster 13 moves downwardly, and the cylinder and piston means 20 moves downwardly therewith to the phantom line position, the point of contact or intersection between the camming plate 25 and live lever 22 moves outwardly along the lever arm 22 away from the pivot pin 32 and towards the center of the cylinder means 20.- That is, when the car is at or near a full load position, the bolster 13 and cylinder means 20 are moved downwardly and are in the dotted line position in FIG. 5 wherein the intersection point between the camming p'late 25 and live lever 22 is at the point 72, so that the effective length of the live lever 22 has increased by the amount of the distance between the contact points 28 and 72.

The piston and cylinder means 20 always exert the same amount of force on the live lever 22. However, the effective length of the lever arm, i.e. from pin 38 to a point on the live lever 22 engaged by the camming plate 25, changes with loading of the railroad car and vertical movement of the bolster. Thus, the moment about the pin 33 changes with changes in the effective lever arm to afford corresponding changes in force on the brake beams and consequently changes in the brake shoe load. Thus, the amount of force with which the brake shoes 55 and 58 engage the treads of the car wheel also change with car loading. In practice, this change of force, i.e. braking force at the wheels, is approximately 14%. Such changes in braking force are particularly advantageous for specially-designed cars now in operation, in that the present invention eliminates, in some cases, the need for an additional and expensive empty load mechanism found necessary to meet accepted AAR standards which call for a maximum brake shoe load not to exceed a certain percentage of the car weight empty, and which call for a minimum brake shoe load not less than another percentage of the total car weight loaded.

The present invention employs a tapered camming plate 25, which extends outwardly from the piston 24 at one distance at its lower end 74, FIG. 6, and extends outwardly at a progressively increasing distance toward its upper end 75. Stated differently, the camming plate 25 is tapered to become wider moving upwardly and forwardly from its lower end 74 to its upper end 75. As will be apparent from FIGS. 4 and 6, the normal disposition of the live lever 22 is to extend further forwardly towards the front axle 15 from the pivot pin 32 to the outer tip 78 of the live lever 22. The increased taper of the camming plate 25 is proportioned to keep the piston stroke or travel of the piston 24 at a constant value with changes in the cont-act point between the camming plate 25 and the liver lever 22. Because of the work (or force times stroke) of the piston must be equal to the work (or force times stroke) at the brake shoes, and nothing has acted to change the distance through which the brake shoes must move to engage the wheels, this increase in brake shoe load can be accomplished only at the expense of increased piston travel unless some means is taken to automatically correct piston travel. The taper of the camming plate 25 accomplishes this function, because as the bolster 13 depresses and the brake shoe load increases the taper of the camming plate 25 causes the live lever 22 to move in a brakes-applied position thus decreasing the shoe-to-wheel clearance.

The contouring, i.e. tapering, of the camming plate 25 is for the purpose of maintaining the piston stroke at a constant value; and the adjusting by the slack adjuster 53 is for wear of the brake shoes. In instances where a manual slack adjuster is employed, as distinguished from the automatic slack adjuster 53 disclosed herein, the camming plate 25 will of itself maintain the piston stroke at its nominal value for varying conditions in loading of the car.

In lieu of the slack adjuster shown in the above identified co-pending application, it is preferred to employ a slack adjuster manufactured by the Ellc-on-National Corporation, the general operating characteristics of which are disclosed in US. Patents Nos. 3,001,612 and 3,037,587.

It is to be understood that when the force from the cylinder is being applied, the upper end 48 of the dead lever 42 pushes with approximately this same amount of force against the pin 50 on the rearwardly extending rack 52 of the slack adjuster 53. Also, when the piston 24 and camming plate 25 move through the'proper or nominal distance, the camming plate 25 moves live lever 22 to engage its bracket 80 with the downwardly bent end 82 of the connecting rod means 68. If the proper amount of force is exerted on the rack 52 prior to the piston moving through its nominal stroke and moving the rod 68, slack adjuster 53 permits continued movement of the piston 24 and. camming plate 25 without increasing the braking pressure by moving the rack 52 into the housing of the slack adjuster. Conversely, the slack adjuster 53 moves the rack 52 rearwardly out of the slack adjuster housing to take up slack when the piston stroke is achieved without the proper brake pressure so that the proper amount of stroke is achieved.

The connecting rod means 68 between the live lever 22 and adjuster 53 is operable by a bracket 80 secured to the live lever 22. The bracket 80 is on the live lever 22 rather than the camming plate 25 to assure that the slack adjuster 53 is operated when the hand brake rod 65 is pulled and the live lever 22 is pivoted thereby. Without the connection on the live lever 22, during a hand braking operation, it would. appear to the slack adjuster 53 as though the braking force was being applied without the piston 24 moving to its proper position, and hence, the slack adjuster 53 would adjust accordingly.

The downwardly bent end 82 of the connecting rod means 68 andthe bracket 80 constitute a one-way connection between the slack adjuster 53 and the live lever 22 to assure proper braking operation by either the camming plate 25 or hand brake linkage. Thus, when the live lever 22 rotates through the predetermined amount of distance, irrespective of whether or not the live lever 22 is being rotated by the camming plate 25 or hand brake linkage, the bracket 80 engages the downturned end 82 of the connecting rod 68 and exerts a force thereon to control adjustment of the positions of the brake beams by the slack adjuster 53.

The connecting rod 68 is guided for sliding movement by a bracket 84 aflixed to the forward end of a housing for the cylinder and piston means 20. The bracket 84 is provided with an additional aperture through which is extended a guiding rod 85, which slides in an aperture in the guiding bracket 84, as the camming plate 25 moves with the piston 24. The guide rod 85 functions to maintain a predetermined angular position between the camming plate 25 and a live lever 22 to prevent turning of the camming plate and turning of the piston 24. That is, the piston 24 would be free to rotate within its cylinder if it was not limited by the guide rod 85 held in the bracket 84.

From the foregoing, it is seen that outward movement of the camming plate 25 upon operation of the fluid cylinder and piston means 20 causes the camming plate 25 to contact and rotate the live lever 22 about its pivot pin 32. The amount of loading on the railroad car controls the vertical position of the bolster 13 and determines the intersecting point between the camming plate 25 and the live lever 22. This intersection point ranges between a lower intersecting point 28 for a lightly loaded or empty car and upper intersection point 72 for a full or heavily loaded car. The increase in effective lever arm with a heavily loaded car provides an increase in moment on the live lever 22 to increase the brake shoe load. Conversely, intersection of the camming plate 25 and live lever 22 for a lightly loaded car is accompanied by a reduced effective lever arm and a reduced moment resulting in a reduced brake shoe load.

It is also seen that the camming plate 25 is profiled or tapered to maintain the nominal stroke with changes in the lever ratios caused changes in car loading. Additionally, the bracket and rod means 68 provide a oneway connection to the slack adjuster 53 to control adjustments made to assure proper braking movements irrespective of operation of the live lever and dead lever either by a piston or by a hand brake mechanism.

Hence, while preferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification, and we therefore do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

We claim:

1. In a truck mounted brake unit adapted to cause braking of railroad car wheels and adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted for vertical movement relative to the side frames of the truck; a pair of brake beams disposed on opposite sides of the bolster, said brake beams being disposed for movement to apply a braking force to the car wheels; operating means for said brake beams including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beams, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston means secured to said bolster and movable vertically with said bolster; and a camming plate secured to said piston means and operable to engage and rotate said live lever, said camming plate engaging said live lever at different contacting points on said live lever as said camming plate moves vertically with said bolster relative to said live lever so that the moment acting on each of the brake beams changes with loading of the railroad car and so that the amount of braking force is changed with changes with loading of the railroad car. I

2. In a truck mounted brake unit adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted for vertical movement relative to the side frames of the truck, a pair of brake beams disposed on opposite sides of the bolster, said brake beams being disposed for movement on said side frames; operating means for said brake beams including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beam-s, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston means se cured to said bolster and movable vertically with said bolster; a camming plate secured to said piston means and operable to intersect and operate said live lever at different points of contact on said live lever as said camming plate moves vertically with said bolster relative to said live lever so that the total moment acting on each of the brake beams changes With loading of the railroad car and changes the amount of braking force afforded by said brake beams, and a slack adjusted means operatively connected to said live and dead levers to maintain said piston stroke.

3. In a truck mounted brake unit adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted for vertical movement relative to the side frames of the truck, a pair of brake beams disposed on opposite sides of the bolster, said brake beams being disposed for movement on said side frames; operating means for said brake beams including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beams, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston means secured to said bolster and movable vertically with said bolster; a camming plate secured to said piston means and operable to intersect and operate said live lever at different points on said live lever as said camming plate moves vertically with said bolster relative to the live lever so that the efie-ctive length of live lever changes with loading of the railroad car and changes the amount of braking force aiforded by said brake beams, a slack adjuster means connected to said dead lever, said slack adjuster means adapted to compensate for slack and to maintain said piston stroke; hand brake operating means operable to move said live lever and to move said brake beams to a braking position; and connection means between said live lever and said slack adjuster means operable to actuate said slack adjuster means.

4. In a truck mounted brake unit adapted to cause braking of railroad car wheels and adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted for vertical movement relative to the side frames of the truck, a pair of brake beams disposed on opposite sides of the bolster, said brake beams being disposed for movement longitudinally of said side frames; operating means for said brake beams including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beams, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston means secured to said bolster and movable vertically with said bolster; and a camming plate secured to said cylinder and piston means and operable to intersect and operate said live lever at different points on said live lever as said camming plate moves vertically with said bolster relative to the live lever so that the total moment acting on the respective brake beam changes with loading of the railroad car and the amount of braking force changes with loading of the railroad car, said camming plate being tapered towards said live lever and being dimensioned to keep the piston stroke constant with changes in vertical relationships between the camming plate and the live lever.

'5. In a truck mounted brake unit adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted tor vertical movement relative to the side frames of the truck, a pair of brake beams disposed on opposite sides of the bolster, said brake beams being disposed for movement on said side trame-s; brake beam operating means including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beams, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston means secured to said bolster and movable vertically with said bolster; a camming plate secured to said cylinder and piston means and operable to intersect and operate said live lever at different points on said live lever as said camming plate moves vertical with said. bolster relative to the live lever so that the eff ctive length of the live lever changes loading of the railroad car and changes the amount of braking force afforded by said brake beams, and a slack adjuster means disposed in sub stantially axial alignment with said piston and cylinder means and operatively connected to said live and dead levers to operate said slack adjuster means to maintain said piston stroke at a constant value.

6. In a truck mounted brake unit adapted to cause braking of railroad car wheels and adapted to be secured to the truck of a railroad car, wherein a bolster of the truck is spring mounted for vertical movement relative to the side frames of the truck, a pair of brake beams disposed on opposite sides of the bolster, said brake beam-s being disposed for movement on said side frames; operating means for said brake beam-s including a live lever pivoted on one of said brake beams, a dead lever pivoted on the other of said brake beams, and a connecting rod between said live lever and said dead lever; an operating cylinder and piston :mea-ns secured to said bolster and movable vertically with said bolster; a camming plate secured to said cylinder and piston means and operable to intersect and operate sa-i-d live lever at different points on said live lever as said camming plate moves vertically with said bolster relative to the live lever so that the efiective length of said live lever changes with loading of the railroad car and changes the amount of braking force afforded by said brake beams, said camming plate being tapered towards said live lever and being dimensioned to keep the piston stroke constant with changes in vertical relationships between the camming plate and the live lever; a reciprocal piston in said piston and cylinder means; and holding means for said camming plate for holding said camming plate in a predetermined orientation so that the taper on the camming plate remains aligned with said live lever.

References Cited by the Examiner UNITED STATES PATENTS DUANE A. REGER, Primary Examiner. 

1. IN A TRUCK MOUNTED BRAKE UNIT ADAPTED TO CAUSE BRAKING OF RAILROAD CAR WHEELS AND ADAPTED TO BE SECURED TO THE TRUCK OF A RAILROAD CAR, WHEREIN A BOLSTER OF THE TRUCK IS SPRING MOUNTED FOR VERTICAL MOVEMENT RELATIVE TO THE SIDE FRAMES OF THE TRUCK; A PAIR OF BRAKE BEAMS DISPOSED ON OPPOSITE SIDES OF THE BOLSTER, SAID BRAKE BEAMS BEING DISPOSED FOR MOVEMENT TO APPLY A BRAKING FORCE TO THE CAR WHEELS; OPERATING MEANS FOR SAID BRAKE BEAMS INCLUDING A LIVE LEVER PIVOTED ON ONE OF SAID BRAKE BEAMS, A DEAD LEVER PIVOTED ON ONE OF SAID BRAKE BEAMS, AND A CONNECTING ROD BETWEEN SAID LIVE LEVER AND SAID DEAD LEVER; AN OPERATING CYLINDER AND PISTON MEANS SECURED TO SAID BOLSTER AND MOVABLE VERTICALLY WITH SAID BOLSTER; AND A CAMMING PLATE SECURED TO SAID PISTON MEANS AND OPERABLE TO ENGAGE AND ROTATE SAID LIVE LEVER, SAID CAMMING PLATE ENGAGING SAID LIVE LEVER AT DIFFERENT CONTACTING POINTS ON SAID LIVE LEVER AS SAID CAMMING PLATE MOVES VERTICALLY WITH SAID BOLSTER RELATIVE TO SAID LIVE LEVER SO THAT THE MOMENT ACTING ON EACH OF THE BRAKE BEAMS CHANGES WITH LOADING OF THE RAILROAD CAR AND SO THAT THE AMOUNT OF BRAKING FORCE IS CHANGED WITH CHANGES WITH LOADING OF THE RAILROAD CAR. 